The present invention relates to an image fixing method of fixing image on a recording medium by applying a predetermined pressure to a developed image formed on the recording medium and an apparatus therefor, which is suitable for use in a facsimile apparatus or the like.
Conventionally, in order to fix an image developed by a dry type development apparatus to a recording medium, with application of a predetermined pressure to the developed image, two calender rollers are disposed so as to be in pressure contact with each other in the direction normal to the movement direction of the recording medium and the recording medium is caused to pass between the two rollers.
In order to obtain a good fixed image by this method, it is necessary to apply a pressure as great as about 700 to 800 kg in total uniformly to the recording medium in the direction of the width thereof, that is, in the direction normal to the movement direction of the recording medium and calender rollers with a diameter as great as 60 to 70 mm are required and the calender rollers have to be in pressure contact with each other, with the axes thereof relatively shifted.
Therefore, the image fixing apparatus of this type tends to become over-sized and over-weighted, so that a great driving force is required for driving the calender rollers and therefore a drive apparatus for driving the calender rollers also tends to become over-sized.
In order to prevent the image fixing apparatus of the above-mentioned type from becoming over-sized, in another conventional image fixing apparatus an auxiliary roller is additionally attached to the two calender rollers to that and it is tried to increase the pressure between the two calender rollers by the auxiliary roller.
According to this method, it becomes unnecessary to use the calender rollers having such a great diameter and consequently the driving force required for driving the calender rollers can be reduced to some extent. However, it requires three rollers and the image fixing apparatus still tends to become over-sized and over-weighted and the size of the roller drive apparatus cannot be reduced so much.
Furthermore, in any of the above-mentioned conventional image fixing apparatuses, pressure always has to be applied uniformly in the direction of the width of the recording medium and accordingly the surface of each calender roller has to be finished accurately. Even if the surface of each calender roller were finished so accurately, when assembling the calender rollers, a high assembling accuracy and a fine adjustment of the image fixing apparatus are required so as to set the space between the two calender rollers uniformly and accurately. Otherwise, the recording medium is wrinkled when the recording medium is caused to pass through the calender rollers. This will reduce the operation efficiency and accordingly a high cost is required.